High Weber Number SMD Correlations for Pressure Atomizers

Published correlations for the Sauter Mean Diameter (SMD) of sprays produced by pressure atomizing injectors have generally taken the form, SMD = Aω˙^B ΔP^C. The system of units and the fuel properties are reflected by the coefficient A. The exponent of the flow rate term (B) has been found to be approximately 0.20. There has been less agreement relative to the appropriate value of the pressure drop exponent (C). Simmons [1] reported the value of the pressure drop exponent to be 0.354, and this value has been widely used. This paper presents recently acquired experimental data that reveal that for We greater than 10.0 a different atomization process occurs, i.e., “shear-type” breakup, which results in much finer atomization than predicted by previously reported correlations. To accurately represent the high We data, a significantly different SMD correlation form is required and is reported in this paper. The effects of large variations in the nozzle size, fuel density, viscosity, surface tension, and fuel temperature have been included in the derivation of the correlations.